38 year old female presents with non blanching rash and menorrhagia
There is a moderately low haemoglobin, with a low MCV and severely low platelets. The white cell count is normal, with normal amount of neutrophils and lymphocytes. There is a normal UEC’s. The bilirubin is elevated with the rest of the LFT’s being normal
In the context of low platelets and a microcytic anaemia, the anaemia could be due to blood loss from menorrhagia secondary to low platelets. The cause of the low platelets are numerous:
-Increased destruction – ITP, DIC, infections (Dengue, Malaria, Rickettsia), drugs (heparin, phenytoin, carbamazepine, valproate, NSAID, immune suppressants…..list is endless), hypersplenism (poral hypertension, sickle cell), TTP, HUS, antiphospholipid syndrome, autoimmune, post transfusion purpura.
-Dilutional – massive transfusion
-Decreased production – haematological malignancies, aplastic anaemia, Vit B12 deficiency, infections, genetic disorders, radiation therapy or chemotherapy.
In this clinical context, the patient has had a recent URTI, therefore the most likely diagnosis would be Idiopathic Thrombocytopaenic Purpura. However the LFT’s give a clue to something more going on – the raised bilirubin would raise the suspicion of a haemolytic anaemia occurring.
Haemolytic Anaemias are divided into intravascular and extravascular and further divided into Immune and Non Immune:
-Intravascular Immune – ABO/Rhesus Incompatibility, Warm and cold Autoimmune haemolytic anaemia due to infections, drugs, autoimmune diseases and lymphoproliferative disorders
-Intravascular Non Immune – MAHA eg envenoming TTP or HUS, Infections, mechanical eg prosthetic valves, trauma
Extravascular – enzyme abnormalities, membrane abnormalities, haemoglobinopathies, hypersplenism.
Further investigations involves confirming haemolysis and identifying the cause:
Haemolysis is confirmed by – increased reticulocyte count, LDH, indirect bilirubin and plasma free haemoglobin
-decreased haptoglobin
-urine haemoglobin and haemosiderin
To identify the cause one needs to look at blood film, Coagulation profile, renal function, G6PD deficiency, Coombs test, ADAMTS 13 level
The above patient had an LDH of 903, Haptoglobin <0.1, normal coagulation profile. The blood film showed reds cells that were slightly microcytic and hypochromic and slight poikilocytosis with fragmented cells, moderate polychromasia and rouleaux formation. White cells and platelets morphology were normal. The haemotologist comment – blood film is of a microangiopathic haemolytic anaemia, most likely diagnosis TTP given the normal renal function and coagulation profile.
The ADAMTS-13 level came back <1% confirming the diagnosis of TTP.
To read more about TTP go to https://emedicine.medscape.com/article/206598-overview#a1